We have already shown a strange behaviour of the VE2 filter – or what appears to be a problem related to the use of the VE2 filter. The post is here.

Now we are able to report something even stranger (OK, just as strange then). We appear to have a relationship between the ‘VE2 pedestal’ and the airmass of the observation:In the upper frame we see the old VE2 pedestal vs exposure time plot. In the lower frame we see that the pedestal is also a function of the airmass! If the pedestal was proportional to airmass we could, perhaps, understand the phenomenon as something showing a flux proportional to the amount of atmosphere (I am thinking of some sort of airglow here) – but NO, the pedestal height is smaller the larger the airmass is!

Is this some electronic problem related to how the telescope is oriented? Then why the inverse proportionality on exposure time too? Why not the other filters?